defmodule Day04 do
def part1(file) when is_binary(file), do: file |> to_grid() |> part1()
def part1(%{} = grid), do: Enum.count(grid, &accessible?(grid, &1))
def to_grid(file), do: file |> Util.file_to_char_map() |> Map.filter(fn {_, v} -> v == ?@ end)
def accessible?(grid, {pos, _}), do: Enum.count(adj(pos), &(grid[&1] == ?@)) < 4
def adj({x, y}), do: for(dx <- -1..1, dy <- -1..1, {dx, dy} != {0, 0}, do: {x + dx, y + dy})
def part2(file) do
to_grid(file)
|> Stream.unfold(fn grid ->
{count, new_grid} = remove_accessible(grid)
if count > 0, do: {count, new_grid}, else: nil
end)
|> Enum.sum()
end
def remove_accessible(grid) do
removable = grid |> Enum.filter(&accessible?(grid, &1)) |> Enum.map(&elem(&1, 0))
{length(removable), Enum.reduce(removable, grid, &Map.delete(&2, &1))}
end
end
billylanchantin
0